An electronically-controlled gasoline injection device with a motor-type fuel pump built therein, has been widely used due to the fact that the device is effective in saving a fuel consumption of an automobile and cleaning an exhaust gas thereof.
A reduction in a size and weight of an automobile engine has become a strong trend in recent years. For this reason, not only a fuel pump such as the one shown in FIG. 3 has been downsized, but a bearing used in such fuel pump has also been either downsized or thin-walled. Meanwhile, a discharging performance of a motor is maintained at the same level as before. That is, it is required that a bearing used in a motor-type fuel pump exhibit a superior wear resistance even when exposed to a high-pressure gasoline flowing at a high speed.
In fact, automobiles have spread across various regions around the world due to the globalization of the automobile market in recent years. However, the qualities of liquid fuels such as gasoline that are used in each country around the world are diverse, and there are regions where coarse gasoline with a large amount of sulfur or an organic acid(s) contained in fuels are used inevitably. Here, as a result of using such coarse gasoline containing sulfur or an organic acid(s), there exists a problem where a bearing of a motor-type fuel pump corrodes due to sulfur and the organic acid(s); and where a life of the bearing shortens due to, for example, a decrease in strength of the bearing or a motor lock trouble.
In order to solve the aforementioned problem, as to a fuel whose impurities contain sulfur or a compound(s) thereof, there have been disclosed in Japanese Unexamined Patent Application Publications No. 2001-192754 and No. 2002-180162, for example, bearings for motor-type fuel pump that comprise a Cu—Ni-based sintered alloy. Further, as to a fuel such as a coarse gasoline containing an organic acid(s) or the like, there has been disclosed in Patent document 3: Japanese Unexamined Patent Application Publication No. 2006-199977, for example, a bearing made of a Cu—Ni-based sintered alloy having a structure in which a Sn highly-concentrated alloy phase is formed.